The question wasn't whether or not say the PS3 version would run on the PS4 (though it won't, and being digiital or not is completely irrelevant), but whether or not they would release a port for next-gen hardware. With very PC-like architecture it would not be difficult to do.

This game is looking really, really sweet and like it'll live up to what they established in Bioshock.

Furthermore, Steam is making it incredibly tempting to buy at the moment what with offering Bioshock and X-COM as pre-purchase prizes... I think I'm going to commit to that... I want X-COM so very badly... and original Bioshock would be awesome too, since I've never owned it, only borrowed. It's a great story and I wanna' go through it again with my gal in tow, cringing all the way haha :D

I bet it's more mundane than you'd hope since it boils down to math in the end. It probably goes by how much code would fit at a certain font size on a page of paper, how many pages it'd take to print that all out, then multiplying that by how long each page is.